feat(status): add StatusCode::try_from(u16).

This is a temporary function until the `TryFrom` trait stabilizes.

BREAKING CHANGE: Removes the undocumented `from_u16` function. Use
  `StatusCode::try_from` instead.

  Also makes the `status` module private. All imports of
  `hyper::status::StatusCode` should be `hyper::StatusCode`.

src/http/mod.rs

@@ -89,7 +89,7 @@ impl RawStatus {
     /// Converts this into a StatusCode.
     #[inline]
     pub fn status(&self) -> StatusCode {
-        StatusCode::from_u16(self.0)
+        StatusCode::try_from(self.0).unwrap()
     }
 }